【作者】 罗振；

【导师】 陈严；

【作者基本信息】 汕头大学 ， 机械电子工程， 2011， 硕士

【摘要】 风力机是承受复杂随机载荷的动力系统,其动态气动弹性问题涉及随机动态气动力与结构动力响应之间的相互作用,是一个含大气边界层湍流风场、风轮动态空气动力学、叶片及机组结构动力学的多学科交叉问题。本文基于国家自然科学基金项目“考虑叶片柔性变形的风力机气动弹性问题研究”,针对现代大型水平轴风力机自身的结构,结合外部运行特点和国际设计标准,应用现代模态分析理论和有限元数值分析相结合的方法,以1.5MW水平轴风力机为对象,研究了大型风力机在空气动力载荷和机械载荷作用下的结构动力学响应分析方法。本论文采用以叶素动量理论为基础的动态气动分析方法来得到气动载荷,建立结构动力学响应模型分析随机气动载荷作用下的结构动态响应及气动弹性载荷。考虑塔架结构变形对叶片的动态反馈作用,并通过模态综合法,实现风轮和塔架的耦合。最后,利用Palmgren Miner线性累积损伤理论来计算风力机的安全疲劳寿命。论文主要包括以下几个方面的内容:(1)分析风力机基本的空气动力特性。根据修正后的叶素动量理论对作用在风轮叶片上气动载荷进行估算。(2)将叶片和塔架简化为变截面悬臂梁,采用二节点梁单元建立其有限元模型。利用多自由度拉格朗日方程建立运动方程,通过模态分析得到固有频率和振型。考虑风轮旋转频率,避免风力机固有频率和激振频率重叠引起共振。(3)运用模态叠加理论和Newmark法来求解运动方程,获得叶片和塔架在载荷作用时的动态响应,并编制相应的计算程序。(4)研究风轮和塔架的耦合方法,考虑塔架变形对风轮动态气动特性影响。计算低阶主导模态,通过模态综合法建立风轮模态和塔架模态的相互联系。考虑它们之间气动弹性的影响,叠加时序的变化,运用迭代算法求得主模态的响应结果。(5)利用雨流计数法统计风力机随机载荷谱和Palmgren-Miner线性累积损伤法则进行叶片疲劳寿命的估算。更多还原

【Abstract】 Wind turbine is a dynamic system that bears complex random load. The problem about aeroelasticity is related to the interaction of stochastic dynamic aerodynamic and structure dynamic response. And it is a multidisciplinary issue about atmospheric boundary layer turbulent wind field, rotor dynamic aerodynamics and blade and unit structural dynamics. In this paper, aimed at the configuration, operation characteristic and international standard of the modern large scale horizontal axis wind turbine, using the method which combines modern modal analysis theory and finite element numerical analysis, targeting a 1.5MW horizontal axis wind turbine, the analysis method of the large scale wind turbine dynamic response caused by the aerodynamic load and mechanical load is investigated based on the NSFC project“Research on the aeroelasticity problem of wind turbine considering the flexible deformation of the blade”.Using blade element momentum theory to calculate aerodynamic load and establishing the structural dynamics model, the structure dynamic response and aeroelasticity load under random aerodynamic load are analysed. At the same time, it should be considered that tower structure deformation has a dynamic feedback to the blade. With the modal synthesis method, the coupling of rotor and tower is achieved. Finally, the security fatigue life of wind turbine based on the Palmgren Miner linear fatigue damage accumulation rule is estimated.The main content of this paper includes the following respects:(1) The basic aerodynamic characteristics of the wind turbine are analysed. According to revised blade element momentum theory, the aerodynamics load on the blade is estimated.(2) The rotor and tower are considered as a cross-section cantilever and appied two-node beam element to the finite element modeling. Multi-DOF Lagrange equations based on the generalized coordinate system is used to build the motion equation. And the modal analysis is used to get natural frequencies and mode shapes. The frequency of the rotating rotor is given and the resonance should be avoided that is caused by the overlap in natural frequency and excited frequency.(3) Mode-superposition method and Newmark method are used to compute the motion equation and determine the dynamic response of the blade and tower under loads. In addition, the numerical programs are developed. (4) Considering that the tower deformation affects the dynamic aerodynamic characteristics of the rotor, the coupling method of the rotor and tower is studied. Low-level lead modes are calculated and the relation between the rotor and tower is established by modal synthesis method. Considering the impact of the aeroelasticity, overlying the timing changes and applying iterative algorithm the response results of lead modes are obtained.(5) The stochastic load spectrum is counted by the rain flow count method. And the fatigue life of the blade is estimated by the Palmgren Miner linear fatigue damage accumulation rule.更多还原